The present invention relates to a printing plate apparatus particularly in one aspect, the invention relates to a presensitized plate (hereinafter referred to as a PS plate) feeding apparatus. Specifically, in this aspect, the invention relates to an apparatus for positioning a PS plate and feeding it to a succeeding process position such as printing process device.
Generally, a PS plate is a photosensitive material manufactured by coating an aluminum body with a photosensitive layer. The PS plate is considerably heavier than other photosensitive plates whose bodies are made of film or paper. For this reason, much manual effort is required to move PS plates rapidly and it is accordingly difficult to properly position such a plate. Therefore, it is desirable to be able to position a PS plate automatically. In addition, it is desired that a positioned PS plate be transferred to a succeeding process position or station without misalignment.
In view of the above-noted deficiencies, an object of the present invention is to provide a PS plate feeding apparatus having front-end positioning means provided in a delivery path of a PS plate which also are used as electrodes, transferring means for changeover from high speed delivery to low speed delivery when the PS plate reaches a predetermined position of the front end positioning means, and feed-out means for transferring the PS plate positioned by the front end positioning means to a succeeding process position, the feed-out means cooperating with the apparatus of the succeeding process position and being removable therefrom.
Another object of the present invention is to provide a plate feeding apparatus capable of feeding a printing material to a predetermined position, namely a printing position on the base plate without obstructing a mechanism for printing on the base plate and a mechanism for removing the printed material.
The present invention also relates to a device for close contact printing of a transparent picture plate such as may be used for printing a film onto a printing material such as a photosensitive film, a resin plate or a metallic plate.
There has been heretofore known a method in which a transparent picture plate is aligned on a printing material on a printing base plate, and a flexible transparent sheet is placed over the aligned picture plate and the printing material, and the inside of the sheet is exhausted by a vacuum pump or the like to thereby place it at a negative pressure and the flexible transparent sheet is squeezed by a squeeze roller to thereby closely contact the picture plate with the printing material. The sheet is then illuminated by light from above to thereby complete the printing process.
It was proposed in Japanese patent application No. 53-49460, which is of common inventionship, that the original picture be fixedly secured to the flexible transparent sheet for printing as described above for the purpose of maintaining contact between the original picture and the printing material and facilitating alignment of the original picture where the same original picture is repeatedly used for printing on the printing material plate to thereby enhance the efficiency of the operation. In this case, the printing material is automatically provided.
Further, the present applicant proposed a close contact printing device as described in Japanese Utility Model Application No. 53-95317. In this device, the original picture is positioned in place on the printing plate aligned on the printing base plate. After the picture is covered with a flexible transparent sheet, the inside of the transparent sheet is sealed using a vacuum method and further the upper surface thereof is squeezed by a squeeze roller to thereby contact the original image with the printing material. It is a feature of such a device, one end of the original picture retained in place on the printing material while the other end is held with an upward tension and that the squeeze roller is movable relatively to the base plate.
However, in a close contact printing device, since the other end of the transparent sheet is held under upward tension as mentioned above, when the squeeze roller is moved relatively in the opposite direction to the base plate in order to restore the flexible transparent sheet by removing the printed material after completion of printing, unless the other end of the flexible transparent sheet is moved at a speed higher than the relative movement speed therebetween, a crease or slack is produced in the flexible sheet and the original picture attached thereto is damaged. There are various techniques available for retaining the flexible sheet using a flexible spring, the gravity force of a movable weight, or a driving source. However, the technique using the movable weight is most desirable in view of cost and maintenance.
In the movable weight technique, if the speed that the squeeze roller is moved relative to the base plate is greater than the dropping speed of the weight, a crease or slack is produced in the flexible transparent sheet. The highest relative speed between the squeeze roller is thus naturally determined by the acceleration of the weight due to gravity.
The velocity of relative movement between the base plate and the squeeze roller for contacting the flexible transparent sheet with the original picture is defined in a range such that air between the printing material and the original picture is exhausted to thereby provide sufficient contact therebetween. Accordingly, it is difficult to attain a high velocity. However, the relative movement velocity for removal of the flexible transparent from the printing material can be enhanced within the range in which the other end of the flexible transparent sheet is maintained under tension.
In the case in which gravity is employed as described above, if the dropping velocity of the movable weight is increased, it is possible to sufficiently increase the relative velocity for removing the flexible transparent sheet from the printing material.
In view of the above noted deficiency, an object of the present invention is to provide a close contact printing device in which an original picture is placed in an overlapping arrangement on a printing plate which is aligned on a base plate, the original picture is covered with a flexible transparent sheet, the inside of the flexible transparent sheet is sealed, and the upper surface thereof is squeezed by a squeeze roller to bring the original picture into close contact with the printing plate. One end of the flexible transparent sheet aligning the original picture with the printing plate is fixed to the base plate while the other end is maintained under tension by a tensioning means. The squeeze roller is movable relative to the base plate. The tensioning means includes a weight movable by gravity. Transmitting means for amplifying the movement of the weight is provided whereby the other end of the flexible transparent sheet can be moved under tension at a higher speed than that at which the weight would fall due to its gravity force alone.